Enhanced pollenizer and method for increasing seedless watermelon yield

ABSTRACT

An enhanced, diploid pollenizer watermelon plant and method used to maximize the yield of triploid seedless watermelons per area. The enhanced pollenizer watermelon plant of the invention is either a hybrid variety, an open-pollinated variety or a synthetic variety, that exhibits the characteristics of small leaves and fruit with a brittle rind that splits when the fruit is overripe or breaks when relatively small physical forces are applied. The watermelon plant of the invention is also preferably characterized by extended flowering duration, thereby increasing the number of triploid watermelon flowers that are pollinated and set fruit. The method for producing a seedless watermelon fruit, includes the steps of providing a pollenizer diploid watermelon plant, extending the duration of flowering of the pollenizer plant while reducing the number of such plants needed to pollenize the same number of triploid watermelon plants, and maximizing dispersal of the pollenizer watermelon plant throughout the field of triploid watermelon plants.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. application Ser. No.10/091,154, filed Mar. 5, 2002. The aforementioned application isincorporated herein by reference in its entirety.

FIELD OF THE INVENTION

This invention is in the field of watermelon breeding, specificallyrelating to diploid watermelons used to pollinate triploid watermelonplants for the commercial production of seedless watermelon fruit, andincludes a novel method for the production of triploid watermelon fruit.

BACKGROUND OF THE INVENTION

Watermelon is an important horticultural crop that accounts for 2% ofthe world area devoted to vegetable crops. There were 6,024,000 acres ofwatermelon grown in the world and 187,000 acres of watermelons grown inthe United States in 1997 (FAO Production Yearbook 51, 1998). Theestimated annual world watermelon value exceeded $7.6 billion when usingthe United States average price for 1995-1997. The United Stateswatermelon crop amounted to over 41 million cwt, from over 174,000harvested acres, and a farm value of over $266 million, accounted for9.2% of the harvested acres, 10.0% of the production, and 3.5% of thevalue of the United States fresh vegetable industry in 1999 (USDAAgricultural Statistics 2001). California was the leading state inwatermelon farm gate value, exceeded $72 million in 2000, due to highpercentage of triploid seedless watermelon grown in California. Seedlesswatermelon receives well above the average price for seeded watermelonsin the market.

The goal of plant breeding is to combine in a single variety or hybridvarious desirable traits. Desirable traits may include resistance todiseases and insects, tolerance to heat and drought, reducing the timeto crop maturity, greater yield, and better agronomic quality. Withmechanical harvesting of many crops, uniformity of plant characteristicssuch as germination and stand establishment, growth rate, and maturity,are important. Other desired traits may include particular nutrientcontent, color, fruit shape, as well as taste characteristics.

As with many different plants, watermelon contains a fruit part and aplant part. Each part contains different traits that are desired byconsumers and/or growers, including such traits as flavor, texture,disease resistance, and appearance traits such as shape and color. Theseedless trait in the watermelon fruit is highly desired by consumers.For production of seedless watermelon, optimum pollinationcharacteristics of the pollinating plant are desired.

Seedless watermelon plants are triploid and must be pollinated by thepollen of diploid watermelon plants. To provide adequate pollinizationof seedless watermelon plants, it is current practice to plant diploidpollenizer plants over approximately 25-33% of the field surface. Theremaining portion of the field is planted with the triploid plants.Thus, to maximize the value of the crop in the field, growers use highyield marketable diploid watermelon varieties, which ultimately competewith the triploid seedless varieties for sun, nutrients, and space.

A pollenizer for seedless watermelon producing small and unmarketablefruits, which are not harvested, has been disclosed (WO00/70933).However, when this pollenizer is used, a lower total yield of marketablefruit is observed when compared to a commercial pollenizer line. Also,the fruits of the pollenizer described in WO00/70933 that are notharvested become hosts for diseases in the future, and their seeds willgerminate and grow into weeds, thus reducing future yields.

The present invention recognizes the need to increase the yield of theseedless watermelon, preferably without loss in total yields ofmarketable fruits. The present invention also recognizes that novelphenotypic characteristics of the diploid pollenizer plants are neededto permit these diploids to be planted in close proximity to thetriploid plants and to share the field surface with the triploid plants,thereby effectively decreasing the surface area of the field requiredfor the diploid pollenizers of the invention. The present invention alsorecognizes the need to minimize the carryover of unharvested pollenizerfruits as weeds into the subsequent season. The present invention alsorecognizes the need to increase the pollenizing capacity of diploidwatermelon plants in order to further decrease the ratio of diploid totriploid plants in the field, thereby also increasing the yield of theseedless watermelon. The present invention also further recognizes theneeds to allow farmers to distinguish the seedless fruits from thefruits of the pollenizer in the field and to provide marketable value tothe pollenizer fruits themselves.

SUMMARY OF THE INVENTION

The present invention uses a novel diploid watermelon to improve currentmethods of commercial production of seedless watermelon and to increaseseedless watermelon yield. According to the invention, there is provideda novel enhanced, pollenizer diploid watermelon (hereinafter referred toas “enhanced pollenizer”) and method for pollinating seedless watermelonplants. The present invention includes an enhanced pollenizercomprising, at maturity, small leaves and bearing brittle fruits. Thesmall leaves allow the enhanced pollenizer to be grown in closeproximity to the triploid watermelon plants without competing with them,thereby increasing yields of seedless fruits. The brittleness of thefruit offers the advantage that unharvested fruits of the pollenizer canbe easily destroyed through conventional field preparation forminimizing carry over as weeds in future plantings.

The enhanced pollenizer of the present invention preferably furthercomprises heavily branching lacy vines (also referred to as heavilybranched open vines) and therefore preferably comprises a high number ofopen (lacy) branches. The leaves of the enhanced pollenizer alsopreferably comprise non-overlapping, deep lobes. The openness of thebranched or lacy vine results, in part, from the distinct small andnon-overlapping, deep lobed leaves. The lacy branches and the smallleaves, preferably with non-overlapping, deep lobes, of the inventionhave the additional advantage to provide more access of bees to theflowers of both the pollenizing and the triploid plant, therebyenhancing transfer of the pollen from enhanced pollenizer watermelon tothe female flowers of the triploid watermelon. Easier access by bees tothe male flowers of the enhanced pollenizer and coupled with a greaterfrequency of male flowers provides a greater pollen source for triploidfruit production.

A second advantage of small leaves, preferably characterized by deep,non-overlapping lobes, is that more sunlight is able to penetrate toadjacent triploid plants. A third advantage of small leaves, preferablycharacterized by deep, non-overlapping lobes, is that these leaves takeup less field area than the substantially larger leaves of the diploidpollenizers currently used in the production of seedless watermelon.Thus, as it is less competitive for light, water and fertilizers, theenhanced pollenizer of the present invention can also be grown closer tothe triploid plants, and it does not need dedicated space to grow. Whenthe enhanced pollenizer and method of the present invention are used,the triploid seedless watermelon are preferably grown in solid rows at astandard spacing, the enhanced pollinizer being then inter-plantedbetween the plants within the rows. This results in significantly highernumbers of triploid plants per acre compared to the number of triploidwatermelon plants that has traditionally been planted, and higher yieldsof seedless fruits.

Preferably, the fruit of the enhanced pollenizer of the presentinvention are small and therefore easier to distinguish from theseedless fruits in the field. Therefore, also according to the presentinvention, there is provided a novel enhanced pollenizer comprisingsmall fruits with brittle rind. The small fruits with brittle rind alsoreduce the load to the plant and allow the plant to continue floweringfor extended periods of time, significantly greater than pollenizerwatermelons that are currently used in the production of seedlesswatermelon. The longer flowering duration of the enhanced pollenizer,compared to traditional pollenizer diploid watermelons, results inincreased fruit set and yield of seedless watermelon. The brittle rindalso offers the advantage that unharvested fruits of the pollenizerquickly decompose in the fields, and can be easily eliminated fromfurther re-production through conventional crop disposal (discing andplowing).

An additional advantage of the enhanced pollinizer of the presentinvention is also that its fruits contain very large amounts of seeds,which can be harvested and sold as edible watermelon seeds for food orfeed uses, or for use in medicines. This provides additional value tothe grower who can harvest and market the fruits of the enhancedpollenizer as such or its seeds.

The present invention also includes an enhanced pollenizer fruit thatweighs approximately in the range of about 2 to 7 lbs, preferably about2 to about 6 lbs, about 2 to about 5 lbs. The average weight for thefruits of the enhanced pollenizer is preferably about 3.2 lbs.

The present invention further includes an enhanced pollenizer fruit rindthat is brittle, breaking under a pressure preferably approximately inthe range of about 7 to about 11 lbs/in². In another preferredembodiment, an enhanced pollenizer fruit rind breaks under a pressureapproximately in the range of about 90 to about 150 g/mm², preferablyabout 100 to about 148 g/mm², preferably about 110 to about 145 g/mm²,preferably about 120 to about 140 g/mm².

The present invention includes an enhanced pollenizer having leaves witha surface area approximately in the range of about 20 to about 70 cm2,preferably about 22.5 to about 50 cm², preferably about 25 to about 40cm². In another preferred embodiment, the average leaf surface area ofthe leaves of the enhanced pollenizer is approximately about 25 to about40 cm², preferably about 27.5 to about 37.5 cm², preferably about 30 toabout 35 cm².

Also included in the invention is a enhanced pollenizer plant forpollinating triploid plants producing seedless watermelon fruit,comprising, at maturity, the characteristics of smaller leaf sizecompared to the watermelon variety Sangria™, wherein the fruit rind ismore brittle than the rind of the variety Sangria™ (a commercial varietyof Syngenta Seeds, Inc.). The enhanced pollenizer preferably furthercomprises small fruits. The leaves of the enhanced pollenizer preferablycomprises deep, non-overlapping lobes.

The pollenizer diploid watermelon of the invention is further enhancedby including resistance to various pests and herbicides via conventionalplant breeding methods or genetic transformation.

The present invention also provides a method for inter-planting enhancedpollenizer plants amongst the triploid watermelon plants in a field in apattern that decreases the ratio of pollenizing plants to triploidplants and increases the field surface for triploid plants. This allowsfor a higher population of triploid plants, than conventional practices,and results in 25-33% higher yield of seedless fruits.

Also included in the present invention is a method of increasing theyield of triploid, seedless watermelon comprising the steps of reducingfruit load of said enhanced pollenizer watermelon, increasing theflowering duration of said pollenizer watermelon, planting said enhancedpollenizer watermelon in a field of triploid watermelon; and harvestingsaid triploid watermelon.

The invention also provides a method of increasing the yield of triploidseedless watermelon plants by using enhanced pollenizer watermelonplants, preferably with small fruits, wherein the fruit as such are notharvested for human consumption. Preferably, the seeds of the fruits ofthe enhanced pollenizer are used as food or feed, or in medicines.

The present invention also provides a method for producing an enhancedpollenizer comprising crossing a first watermelon plant having smallleaves with a second watermelon plant producing fruit with brittle rindthat splits easily and selecting for a watermelon plant having thecharacteristics of the enhanced pollenizer disclosed herein. Preferably,the first watermelon plant further comprises the characteristic of aheavily branching lacy vine. Preferably, the leaves of the enhancedpollenizer preferably comprises deep, non-overlapping lobes. Preferably,the first watermelon plant has the characteristics of OW824 disclosedherein. Preferably, the second watermelon plant bears small fruit.Preferably, the second watermelon plant has the characteristics of OW823disclosed herein. In a preferred embodiment, the first watermelon plantis OW824. In a preferred embodiment, the second watermelon plant isOW823. In another preferred embodiment, the first watermelon plant isOW824 and the second watermelon plant is OW823. The method preferablyfurther comprises fixing the traits of the enhanced pollenizer.

The present invention also discloses a watermelon enhanced pollenizerobtainable by a method comprising the steps of a) crossing a watermelonplant with a plant of NO1F3203B deposited under Accession No. PTA-4856,b) obtaining a progeny, c) selecting said progeny for thecharacteristics of the enhanced pollenizer, preferably small leaves andbrittle fruit, In a preferred embodiment, it is further selected forheavily branching lacy vines, preferably for small fruit. In a preferredembodiment, the method further comprises crossing said progeny eitherwith itself or with a plant of NO1F3203B, or with another enhancedpollenizer, and selecting for the said characteristics of the enhancedpollenizer. The method preferably further comprises fixing the traits ofthe enhanced pollenizer.

DESCRIPTION OF THE DRAWINGS

FIG. 1 is a photographic depiction of a leaf of the enhanced pollenizerplant of the invention.

FIG. 2 is a photographic depiction of a leaf of the pollenizer referredto as Sangria™ that is currently used in commerce.

DETAILED DESCRIPTION OF THE INVENTION

Development of Seedless Watermelons

Triploid watermelons are created by crossing a tetraploid (4×) femaleparent line with diploid (2×) male parent line. The resulting triploid(3×) watermelon seeds are planted in a field with diploid watermelonpollenizers. The resulting fruit of the triploid watermelon areseedless.

To create a tetraploid female watermelon line, it is known in the art touse chemicals that alter mitosis of a diploid inbred line so thatunusual numbers of chromosomes are obtained. For example, colchicine isa chemical that alters the mitotic spindle fibers of diploid cellsresulting in a number of cells that are tetraploid. The diploid lineused to create a tetraploid is selected based on the traits desired forthe tetraploid line. Traits that are desired for a tetraploid line maytherefore first be introgressed into the diploid inbred lines that willbe used to develop the tetraploid lines by breeding methods well knownto those skilled in the art. Thus, the diploid and tetraploid parentlines are bred separately for the desired traits.

It usually requires at least two generations of self-pollination andselection to “fix” the 4× condition, after the colchicine treatmentgeneration because, often, chromosomal aberrations are encountered thataffect seed fertility, and must be eliminated. Once the stabletetraploid containing the desired characteristics is verified, it thencan be used as a stable female parent for the production of the triploidhybrid. A stable diploid inbred is selected for use as the male parent.Methods for developing tetraploid plants are described in Kihara, H.,1951, Triploid Watermelons, Proceedings of American Society forHorticultural Science 58:217-230; and Eigsti, O. J., 1971, SeedlessTriploids, HortScience 6, pgs. 1-2.

The tetraploid female parent line and diploid male parent line areplanted in a seed production field. The pollen of the diploid maleparent is transferred to the female tetraploid flower by methods wellknown to those skilled in the art. The triploid seed that is produced ispresent in the resulting fruit and is planted to produce the triploidplants. The breeding of watermelon is further described in Mark Bassett(Editor), 1986, Breeding Vegetable Crops, AVI Publishing, ISBN0-87055499-9.

A triploid seedless watermelon is a true F1 hybrid between a tetraploidwatermelon, as the female parent, and a diploid watermelon, as the maleparent (Kihara, H. 1951. Triploid Watermelons. Proceedings of AmericanSociety for Horticultural Science 58:217-230). The seedless condition intriploid watermelon is the result of the presence of three homologoussets of chromosomes per somatic cell rather than the usual two. Cellswith three sets of homologous chromosomes are said to be triploid andare designated as 3×. The triploid seedless watermelons have 33chromosomes (2N=3×=33) in their somatic cells. The inability of thetriploid zygote to produce normal viable gametes (pollen and egg cells)causes the absence of seeds in triploid fruits. Typically, seedlesswatermelons contain small edible white ovules, similar to those inimmature cucumbers.

Adequate viable pollen supply from the diploid pollenizer watermelon isessential for the triploid female flowers to set and develop intoregular seedless fruit. The female flowers of triploid watermelon willnot set if they are not pollinated by viable pollen of diploidwatermelon. (Maynard, D. N. (editor), 2001, Watermelons:Characteristics, Production and Marketing, ASHS Press, ISBN0-9707546-1-2). The diploid watermelon grown in a field of triploidplants is referred to herein as the “pollenizer.” In current commercialtriploid watermelon production fields, the triploid watermelon anddiploid pollenizer are inter-planted, either within row or between rows,in a ratio of approximately 1 diploid to 2 or 3 triploids. Althoughresearch has indicated a 1:4 ratio is acceptable, it is rarely used incommercial plots. (NeSmith, D. S., Duval, J. R. Fruit Set of TriploidWatermelons as a Function of Distance from a Diploid Pollenizer,HortScience 36(1): 60-61, 2001)

Development of Enhanced Pollenizer Diploid Watermelon

According to the present invention, a watermelon (OW824) is selectedhaving the characteristics of a heavily branching lacy vine, early andprolific male flowers, and small leaves with deep, non-overlapping leaflobes. In this example, the fruit of OW824 is relatively large, the rindand flesh are very firm, the seed size is very big and the flesh iswhite. OW824 is a publicly available edible seed watermelon varietygenerally referred to as XinJiang edible seed watermelon.

Also according to the invention, a hybrid watermelon (OW823) is selectedfor its small fruit (2-3 kg) with brittle rind that splits easily. OW823also includes the characteristics of mid-sized seeds with yellow fleshand has relatively large leaves. OW823 is a commercially availablevariety, Tiny Orchid, from Known-You Seeds, Ltd. of Taiwan.

Crossing OW824×OW823 generated progeny having the characteristics of theenhanced pollenizer diploid watermelon of the present invention asdescribed in more detail below.

The initial cross of OW824×OW823 was made during the summer of 2000 inCalifornia. The F₁ generation was grown in the greenhouse in the fall of2000. The F₂ population was grown Florida in the spring, and inCalifornia in the summer of 2001. Individuals with the set of traitsrequired for the enhanced pollenizer were successfully identified andself-pollinated in F₂ populations grown in both locations. A total 7selections were made. The 7 F₃ lines were grown in the field in Floridaand the greenhouse in California in the fall of 2001 for furtherselection and evaluation. Three F₃ lines were identified to best meetour breeding goals and advanced to F₄ generation. They all have the setof the traits required by the enhanced pollenizer. One line, NO1F3203B,now called SP1, is fixed for every trait concerned. NO1F3203B containsthe traits that are illustrative of the traits of the enhancedpollenizer of the invention. Other enhanced pollenizer lines withsimilar characteristics were for example SP2 with slightly larger leavesthan SP1, and SP3 with slightly larger fruits than SP1 and a differentfruit skin color.

Leaf: The leaves of the enhanced pollenizer are significantly smallerand are more numerous than that of the commonly used pollenizers such asthe variety Sangria™ (See FIGS. 1 and 2). The leaves of the enhancedpollenizer preferably have a surface area approximately in the range ofabout 20 to about 70 cm2, preferably about 22.5 to about 50 cm²,preferably about 25 to about 40 cm². In another preferred embodiment,the average leaf surface area of the leaves of the enhanced pollenizeris approximately about 25 to about 40 cm², preferably about 27.5 toabout 37.5 cm², preferably about 30 to about 35 cm². The leaves of theenhanced pollenizer preferably have deep, non-overlapping leaf lobes.

The leaf surface areas of the enhanced pollenizer NO1F3203B and theSangria™, a pollenizer favored by growers, are shown for comparisonpurposes in Table 1. The leaves for both NO1F3203B and Sangria™ weretaken from mature plants sowed on Aug. 20, 2001 and harvested on Nov. 8,2001. TABLE 1 NO1F3203B LEAF cm² SANGRIA LEAF cm² A 38.75 A 232.00 B26.25 B 447.25 C 39.75 C 241.50 D 28.75 D 238.00 E 38.25 E 211.00 F26.27 33.08 (±6.46) 273.95 (±97.60)

The surface area of the enhanced pollenizer leaf of the invention isapproximately 5 to 12 times less than the surface area of the typicaldiploid pollenizer, Sangria™ plant.

FIG. 1 illustrates the non-overlapping characteristic of the deep,non-overlapping lobed leaves of the enhanced pollenizer. Clearly, due tovarious environmental and physical forces, some of the leaves in thispopulation may have some overlapping lobes, but overlapping lobes arenot characteristic thereof. In contrast, the Sangria™ leaf shown in FIG.2 is characterized as having leaf lobes that habitually overlap eachother. The small, deeply lobed and non-overlapping leaves of theinvention allow more sunlight through to adjacent triploid watermelonplants.

Branching: The enhanced pollenizer of the invention is preferably alsoheavily branched (also referred to as “lacy vined” or “open vines”),having significantly more branches (average of 25.9) than the varietyreferred to as Sangria™, (average of 13). The lacy vine characteristicenables the enhanced pollenizer to produce more accessible male flowersthan current diploid pollenizers, thereby enhancing exposure of theflowers to bees. The open or lacy vines also permit the interplanting ofthe enhanced pollenizer between triploid plants thereby allowing forhigher triploid populations and greater seedless fruit production.

Fruit: The fruit rind of the enhanced pollenizer is very brittle and iseasily broken. The brittle fruit rind splits easily, due to naturalmaturation or by breaking or splitting of the fruit during harvest ofthe seedless triploid watermelon (for example from foot traffic).Splitting of fruit signals the plant that it hasn't completed itsreproductive process inducing the plant to continue flowering for alonger period of time. Brittleness is conferred by a gene e (explosiverind, thin, and tender rind, bursting when cut (Rhodes & Dane, 1999,Gene List for Watermelon, Cucurbit Genetics Cooperative Report22:71-77). When measured by a penetrometer, the NO1F3203B breaks atabout 7-11 lbs/in², whereas a typical watermelon such as Sangria™ breaksat about 21-27 lbs/in². Using a Tester FT02 of Wagner Instruments,Greenwich, Conn. 06836, the fruit of the enhanced pollenizer preferablybreaks under a pressure approximately in the range of about 90 to about150 g/mm², preferably about 100 to about 148 g/mm², preferably about 110to about 145 g/mm², preferably about 120 to about 140 g/mm². Bycomparison, the fruit of Sangria™ breaks under a pressure ofapproximately about 300 g/mm².

Preferably, the fruit size of the enhanced pollenizer is approximatelyin the range of about 5 to about 7 inches long×about 6 to about 8 incheswide. Preferably, the fruit size of the enhanced pollenizer isapproximately about 6 inches long×about 7 inches wide, whereas thetypical pollenizer is about 10 inches long×20 inches wide. Small fruitsize, as well its brittleness was selected to decrease the load on theplant, thereby extending the duration of plant growth and flowerproduction. Another advantage of the small fruit size is that it enablesthe harvester to easily distinguish the seedless fruit from seededfruit, is often difficult with currently used pollenizers, which areselected based on their overall similarity to the seedless triploidplants. The fruit of the enhanced pollenizer weighs approximately in therange of about 2 to about 7 lbs, preferably about 2 to about 6 lbs,preferably about 2 to about 5 lbs. The average weight for the fruits ofthe enhanced pollenizer is preferably about 3.2 lbs.

The rind color of the enhanced pollenizer is preferably light green withvery thin dark green lines. The fruit of the enhanced pollenizer of theinvention can be distinguished from the fruit of most (about 99%) of thecommercially available seedless watermelon varieties.

Flowering: The plants of the enhanced pollenizer, e.g. of NO1F3203B,also flower approximately 7 to 10 days earlier than diploid pollenizerplants currently used for the production of seedless watermelon, andcontinue flowering during fruit harvest time of the seedless watermelon,2 to 3 weeks longer than standard diploid pollenizer plants. Thus, thepollenizer plant of the invention has a flowering duration that isapproximately 3 to 5 weeks longer than pollenizers currently used.

Other Traits: The enhanced pollenizer, e.g. NO1F3203B, can be usedeither as donor of the set of traits disclosed above, or as therecurrent parent to develop additional enhanced pollenizer lines. Inaccordance with the invention, the enhanced pollenizer watermeloncontains traits of disease resistance (e.g. Fusarium wilt, Anthracnose,Gummy Stem Blight, Powdery Mildew, and Bacterial Fruit Blotch), insectresistance (e.g. cucumber beetle, aphids, white flies and mites), salttolerance, cold tolerance and/or herbicide resistance added. Thesetraits can be added to existing lines by using either conventionalbackcrossing method, pedigree breeding method or genetic transformation.The methods of conventional watermelon breeding are taught in severalreference books, e.g. Maynard, D. N. (editor), 2001, WATERMELONSCharacteristics, Production and Marketing, ASHS Press; Mohr, H. C.,Watermelon Breeding, in Mark J. Bassett (editor), 1986, BreedingVegetable Crops, AVI Publishing Company, Inc. General methods of genetictransformation can be learned from publish references, e.g. Glich etal., (Eds), 1993, Methods in Plant Molecular Biology & Biotechnology,CRC Press, and more specifically for watermelon in WO02/14523.

Forms of the Enhanced Diploid Pollenizer: Once the enhanced pollenizerlines are developed, several forms of enhanced pollenizer varieties canbe used in commercial seedless watermelon production. Specifically,these forms of enhanced pollenizer varieties include: Forms of EnhancedPollenizer: (1) Open Pollinated Variety: The stable, enhanced lines ofthe enhanced pollenizer are grown in isolated fields, at least 2,000meters from other watermelon varieties. Pollination is conducted in theopen fields by bees. Seeds are harvested from the seed production fieldwhen the fruit and seeds are fully developed. The seeds are dried andprocessed according to the regular watermelon seed handling procedures.(2) Synthetic Variety: The seed of different enhanced pollenizer linesare individually produced in isolated fields. Bee pollination is used ineach isolation. The seed of different enhanced pollenizer are separatelyharvested and processed. Mixing several enhanced pollenizer lines invarious ratios forms the synthetic varieties. The synthetic variety canprovide a broader pollenizer population for the triploid watermelons.(3) Open-Pollinated Hybrid Variety: Two or several enhanced pollenizerlines are planted in the same seed production field with beepollination. The harvested seed lot, therefore, contains both hybrid andinbred seed. (4) Hybrid Variety: Two enhanced pollenizer lines, the maleand female parents, are planted in the same field. Hand pollination isconducted. Only the seed from female parent line is harvested and soldto the commercial grower to use as pollenizer. Table 3 in Example 7shows the results obtained using various combinations of inbred andhybrid enhanced pollenizers.

Method of Seedless Watermelon Production: Most current commercialseedless watermelon growers in NAFTA use elongated diploid varietieswith an Allsweet stripe pattern: light green skin with wide greenstripes, as the pollenizer. The variety referred to as Sangria™ is themost preferred Allsweet type pollenizer and is available as a commercialproduct from Syngenta Seeds, Inc., Boise Id. Typically, the pollenizeris inter-planted with the triploid watermelon either between rows orwithin row. The current method of planting diploid pollenizers includeplanting the diploid plants at a distance from adjacent triploid suchthat they have the same field area available per plant as the field areathat is available to the triploid watermelon plants. For example,currently watermelon growers inter-plant the diploids within a row,whereby the space between all adjacent plants within the row areapproximately equidistant.

Alternatively, diploid pollenizer plants are planted in separate rowsbetween rows of triploid watermelon plants. All rows of diploid andtriploid plants in such a field are planted approximately equidistantfrom each other. In other words, under current methods for producingseedless watermelon, the width of all diploid and triploid rows is thesame.

The method of the present invention includes planting the enhancedpollenizer watermelon plants in rows that are narrower than the triploidrows, thereby saving field area for production of triploid seedlesswatermelon.

Table 2 below shows different planting alternatives for watermelonpollenizer, including a preferred interplanting according to the presentinvention (right column). TABLE 2 Conventional 2:1 Conventional 2:1pollenizer ratio using Pollenizer inter-planted pollenizer ratio usingthe within row method at a 3:1 pollenizer ratio the row method Seeded =◯ Pollenizer = ♦ seeded seedless seedless seeded seedless seedlessseeded Seedless = X Seedless = X ◯ X X ◯ X X ◯ X ◯ X X ◯ X X X X X X X XX ♦ ♦ ◯ X X ◯ X X ◯ ◯ X X ◯ X X ◯ X X X X X X X ♦ ♦ ♦ ◯ X X ◯ X X ◯ X X◯ X X ◯ X X X X X X X X ♦ ♦ ◯ X X ◯ X X ◯ X ◯ X X ◯ X X X X X X X X X ♦♦ ◯ X X ◯ X X ◯ ◯ X X ◯ X X ◯ X X X X X X X ♦ ♦ ♦ ◯ X X ◯ X X ◯ X X ◯ XX ◯ X X X X X X X X ♦ ♦ ◯ X X ◯ X X ◯ X ◯ X X ◯ X X X X X X X X X ♦ ♦ ◯X X ◯ X X ◯ ◯ X X ◯ X X ◯ X X X X X X X

EXAMPLES

The following Examples are provided to illustrate the present invention,and should not be construed as limiting thereof.

Example 1

Triploid watermelon plants are planted in parallel rows 7 feet apart and3 feet apart within each row. However, the enhanced diploid watermelonplants are planted in a narrow row 3.5′ wide (½ the width of thetriploid rows) between every second and third triploid row. For example,rows A and B are two consecutive rows of triploids, each 7-foot wide.Row C is a diploid row that is 3.5 feet wide. Row D and E are thefollowing two 7 foot wide rows of triploids, followed by the 3.5-footwide row F of diploid plants. This pattern is repeated across the widthof the field. Because the diploid row is narrower according to themethod of the invention, the distance between rows B and D is 10.5 feetinstead of the traditional distance of 14 feet. Using this ratio of 1pollenizer row for every 2 triploid rows (1:2), 33.3% of the field wouldnormally be used for the pollenizer plants. Reducing the width of thepollenizer row according to the method of the invention by one-half, thegain of space for planting additional triploid plants would be 33.3%/2or approximately 17%.

Example 2

Triploid watermelon plants are again planted in parallel rows 7 feetapart and 3 feet apart within each row. As in Example 1, the enhanceddiploid watermelon plants are planted in a narrow row 3.5′ wide, but areplanted between every third and fourth triploid row. For example, rowsA, B, and C, are three consecutive rows of triploids, each row being 7′wide. The following row D is a diploid row that is 3.5 feet wide. Row E,F, and G are the following three rows of triploids, all 7 feet wide,followed by a 3.5 foot wide row of enhanced pollenizer plants. Thispattern is repeated across the width of the field. Because the diploidrow is narrower according to the method of the invention, the distancebetween rows B and D is again 10.5 feet instead of the traditionaldistance of 14 feet. Using this ratio of 1 pollenizer row for every 3triploid rows (1:3), 25% of the field would normally be used for thepollenizer plants. Reducing the width of the pollenizer row according tothe method of the invention by one-half, the gain of space for plantingadditional triploid plants would be 25%/2 or approximately 12%.

Example 3

Triploid watermelons are planted in parallel rows 8 feet apart and 3feet apart within each row. The enhanced diploid watermelon plants areplanted in a narrow row 4.0 feet wide (½ the width of the triploid rows)between every second and third triploid row. For example, rows A and Bare two consecutive rows of triploids, each 8 foot wide. Row C is adiploid row that is 4.0 feet wide. Row D and E are the following two 8foot wide rows of triploids, followed by the 4.0 foot wide row F ofdiploid plants. This pattern is repeated across the width of the field.Because the diploid row is narrower according to the method of theinvention, the distance between rows B and D is 12.0 feet instead of thetraditional distance of 16 feet. Using this ratio of 1 pollenizer rowfor every 2 triploid rows (1:2), 33.3% of the field would normally beused for the pollenizer plants. Reducing the width of the pollenizer rowaccording to the method of the invention by one-half, the gain of spacefor planting additional triploid plants would be 33.3%/2 orapproximately 17%.

Example 4

Referring to the above three examples, when triploids are planted inrows 8 feet apart, and the ratio of diploid to triploid is 1:3, it isnow clear that the reduction of the pollenizer row width by one-halfwill gain space for planting additional 12%.

Example 5

It is also within the scope of the invention to reduce the pollenizerrow width to approximately ⅓ that of the triploid row width. Thus,according to the present invention, at any row width, when the ratio ofdiploid rows to triploid rows is:

(a) 1:2, the savings of field area for additional triploid plants is(33%×⅔) or 22%.

(b) 1:3, the savings of field area for additional triploid plants is(25%×⅔) or 16.5%.

(c) 1:4, the savings of field area for additional triploid plants is(20%×⅔) or 13.2%.

It is also within the scope of the invention to reduce the pollenizerrow width to approximately ⅔ that of the triploid row width.

Example 6

It is also within the scope of the present invention to inter-plant thediploid plants within the rows of triploid plants. According to theinvention, the triploid plants are first planted by machine or by handin regularly spaced rows. The triploid plants within each row areplanted, for example, 3 feet apart. After the triploid plants are in thefield as described, the diploid pollenizer watermelon plants of theinvention are inter-planted, by hand, within each row approximatelymidway between the triploid plants. Thus, in this example, the diploidplants are planted approximately 1.5 feet from the flanking triploidplants within the row. Due to the characteristics of the enhancedpollenizer of the invention, the diploid plants can be inter-plantedwithin each row after every 2, 3, 4, 5, 6, 7, 8, 9, or 10 consecutivetriploid plants. It is currently preferred in the industry to plant thediploid plants after every 2 (1:2) or 3 (1:3) triploid plants within therow. A 1:4 ratio has been reported, but is not normally used incommercial fields due to inadequate pollenization of the triploidplants. The field area saved under this example, when compared with boththe current methods of planting diploids in separate rows or within arow at the ratios (diploid:triploid) of:

(a) 1:2, is 33.3%,

(b) 1:3, is 25%,

(c) 1:4, is 20%.

The enhanced pollenizer and method of the present invention comprisesplanting the enhanced pollenizer watermelons in rows that are narrowerthan the rows containing the triploid plants. Although the narrowerdiploid row will encourage diploid plant growth into the triploid plantrow, the novel characteristics of the enhanced pollenizer watermelonallow it maintain its ability to sufficiently pollinate the triploidplants in the field. Thus, the enhanced pollenizer watermelon and methodof the present invention increase the yield of seedless watermelon in afield.

Example 7

A split-plot design is used for this experiment to test three inbredenhanced pollenizers and three hybrid enhanced pollenizers against thecommercial checks Sangria 2:1 and Sangria 3:1. All 6 enhancedpollenizers are inserted between regularly spaced (80″×24″) triploidplants in the ratio of 3:1. For Sangria 2:1 ratio, every third space isa Sangria plant. For Sangria 3:1 ratio, every 4^(th) space is a Sangriaplant. A 5:1 ratio is also included in this trial using the mixedenhanced pollenizers. In this treatment, the enhanced pollenizers plantis inserted between 5^(th) and 6^(th) regularly spaced triploid plants.So there are total 9 main plots, the 9 main treatments/pollinators, inthis experiment. The 9 main plots are separated by cantaloupe plants. 3different triploids, the sub-plots, with 2 replications are used to testdifferent pollinators (see table 3). Plants are well grown except theleaf-miner damage. This damage results in smaller fruit size for Palomarand Tri-X-313. The trials are evaluated after about two months. Thenumber of triploid fruit in each sub-plot is counted. The first 15fruits in each sub-plot are non-selectively harvested and weighted. 10fruits are also harvested from each pollinator and measured for rindfirmness. Data are analyzed using S-Plus 6.1. The enhanced pollenizersvarieties are also evaluated for fruit size and other fruitcharacteristics.

As shown in table 3, very similar fruit set per plant is achieved forall the pollenizer used. Smaller triploid seedless melons are producedwhen Sangria is used as pollinator in the ratio of 2:1 in thisexperiment. This could be due to Sangria's strong competition to thetriploid plant for space, water and nutrient. A lot more seedless melonsper acre, 25% (compared to the 3:1 ratio) to 33% (compared to thestandard 2:1 ratio), are produced when enhanced pollenizers varietiesare used as pollenizer.

The rind of enhanced pollenizer varieties of the present invention ismuch less durable compared to diploid pollenizer Sangria, as indicatedby the force used to penetrate the rind using a fruit firmness tester(Fruit Firmness Tester FT02 of Wagner Instruments, Greenwich, Conn.06836). Should the pollenizer not be harvested for its commercial value,its brittle rind allows the pollinator fruit to be destroyed duringfruit harvest or soon thereafter. This is helpful for unloading thepollenizer plant and maintaining the flowering ability of the pollenizerplants for longer period of time. The brittle rind of the enhancedpollenizer also reduces the risk of carry-over into the next season, asa weed, since the fruit, and plant debris can be easily destroyed, afterharvest of the triploid fruit.

Enhanced pollenizer plants flower about 7 days earlier than diploidSangria. Enhanced pollenizer plants produce more than twice many ofbranches compared to Sangria. This allows enhanced pollenizer plants toproduce more male flowers, thereby reducing the number of pollenizerplants needed. The vine of enhanced pollenizer plant is much thinnerthan regular diploid plants. The leaf size and leaf-lobe size ofenhanced pollenizer are much smaller than those of Sangria. All thesemake enhanced pollenizer much less competitive for light, water andfertilizer, compared to regular diploid watermelon.

Enhanced pollenizer plants are producing male flowers after the harvestof triploid seedless fruits. This gives the potential of having a secondfruit set and multiple harvests of triploid seedless fruit with singleplanting. The male flowers open earlier in the morning compared toregular watermelons, especially in the cooler days. TABLE 3 SeedlessWatermelon Fruit Yields Produced by Using Different Pollenizer and RindFirmness of Different Pollenizer Rind Fruit/Plant Fruit/Acre Frt Wt(lbs) Firmness (g/ Pollinator Palomar RWT8124 TriX313 Mean PalomarRWT8124 TriX313 Mean Palomar RWT8124 TriX313 Mean mm²) SP Hyb 5:1 2.003.60 2.15 2.58 6534 11652 6957 8381 13.6 6.0 15.4 11.6 NA SP1 2.05 3.551.95 2.53 6719 11661 6413 8265 12.2 5.7 14.6 10.8 121 SP1 × SP3 2.003.60 2.15 2.58 6579 11752 7001 8444 13.2 6.0 14.9 11.3 139 SP2 1.90 3.501.90 2.43 6258 11479 6137 7958 12.1 6.0 13.3 10.5 123 SP2 × SP1 1.853.30 2.20 2.45 6004 10728 7106 7946 13.1 5.8 14.0 10.9 129 SP3 1.90 3.401.55 2.28 6210 11170 5116 7499 12.8 6.0 14.1 11.0 133 SP3 × SP2 1.903.60 2.05 2.52 6219 11649 6577 8149 12.5 5.8 13.9 10.7 129 Sangria 2:11.90 3.50 2.00 2.47 4086 7596 4375 5352 10.5 5.7 12.5 9.6 302 Sangria3:1 1.95 3.35 1.95 2.42 4737 8248 4863 5949 12.4 5.6 12.9 10.3 Mean 1.953.52 2.02 2.49 5770 10405 5946 7374 12.5 5.8 13.8 10.7 154 FactorP-value P-value P-value P-value Pollinator 0.0239 0.0000 0.0000 0.0000Triploid 0.0000 0.0000 0.0000 Pollinator * Triploid 0.4121 0.0061 0.0029Replication 0.9372 0.8580 0.6310

Example 8

Eight triploid varieties (see table 4) are transplanted on two 80″ bedsand spaced 24″ apart. These two beds are located in the center of ourregular hybrid evaluation block. A diploid hybrid bed is placed in eachside of the two trial beds to eliminate the pollination factor. About 90plants are transplanted for each variety. Two days later, each triploidplot is divided into 2 sub-plots and the enhanced pollenizer SP1 plantsof the present invention are inserted in one of the 2 sub-plots in theratio of 3:1, for each of the 8 triploid varieties. This plantingpattern allows 3260 triploid plants per acre. The 8 triploid varietiesdiffer in fruit shape, size and maturity. About 10 weeks later, thefirst 30 fruits are non-selectively harvested from each sub-plot and areweighted using a digital scale. Data are analyzed using S-Plus 6.1.

As shown in table 4, the fruit size differences are solely due totriploid variety differences. Inserting of enhanced pollenizer SP1between regularly spaced triploid plants in the ratio of 3:1 does notreduce the fruit size of triploid seedless fruit, regardless of the typeof triploid variety. The triploid varieties used in this trial representa very broad spectrum of triploids used in commercial production. Theydiffer in fruit size, fruit shape, and maturity. Thus, insertingenhanced pollenizer plants of the present invention between regularlyspaced triploid plants does not reduce the fruit size of the triploidseedless melons. Therefore, a seedless grower can plant his or herfields solid with triploid plants and then insert the enhancedpollenizer plants in a ratio of 3:1 or less. This planting pattern andratio allows growers to produce significant higher (25 to 33%) yields ofseedless fruit per acre. TABLE 4 Effect of Inserting Super-PollenizerBetween Regularly Spaced (80″ × 24″) Triploid Plants in the Ratio of 3:1to the Fruit Size of Eight Different Triploid Watermelon VarietiesSuper-Pollenizer Insertion Triploid Variety No Yes Mean 3X Sangria 18.0518.51 18.28 Palomar 14.23 16.21 15.22 RWT 8126 16.97 17.15 17.06 RWT81246.26 6.03 6.15 RWT8139 15.46 14.43 14.94 RWT8140 15.31 15.73 15.52Shadow 15.97 14.73 15.35 Tri-X-313 15.77 15.60 15.69 Mean 14.75 14.8014.77 Factor P-Value Triploid Variety 0.0000 Super-Pollenizer 0.8829Variety * Super-Pollenizer 0.2451Deposit

Applicants have made a deposit of at least 2500 seeds of enhancedwatermelon pollenizer line NO1F3203B (now called SP1) with the AmericanType Culture Collection (ATCC), Manassas, Va., 20110-2209 U.S.A., ATCCDeposit No: PTA-4856. This deposit of the enhanced watermelon pollenizerline NO1F3203B/SP1 will be maintained in the ATCC depository, which is apublic depository, for a period of 30 years, or 5 years after the mostrecent request, or for the effective life of the patent, whichever islonger, and will be replaced if it becomes nonviable during that period.Additionally, Applicants have satisfied all the requirements of 37C.F.R. §§1.801-1.809, including providing an indication of the viabilityof the sample. Applicants impose no restrictions on the availability ofthe deposited material from the ATCC; however, Applicants have noauthority to waive any restrictions imposed by law on the transfer ofbiological material or its transportation in commerce. Applicants do notwaive any infringement of its rights granted under this patent or underthe Plant Variety Protection Act (7 USC 2321 et seq.).

The foregoing invention has been described in detail by way ofillustration and example for purposes of clarity and understanding.However, it will be obvious that certain changes and modifications suchas single gene modifications and mutations, somaclonal variants, variantindividuals selected from large populations of the plants of the instantinbred and the like may be practiced within the scope of the invention,as limited only by the scope of the appended claims. Thus, although theforegoing invention has been described in some detail in this document,it will be obvious that changes and modification may be practiced withinthe scope of the invention, as limited only by the scope of the appendedclaims.

All references cited herein are incorporated by reference in theapplication in their entireties.

1-52. (canceled)
 53. A method of increasing the yield of triploidwatermelon plants comprising the steps of: a) obtaining a pollenizerwatermelon plant for pollenizing said triploid watermelon plants, saidpollenizer watermelon having the characteristics of: i) reduced fruitload; ii) decreased size of the leaves; iii) increased floweringduration; b) planting said pollenizer watermelon plant in a field oftriploid watermelon plants; and c) harvesting said triploid watermelon.54. A method of increasing the yield of triploid watermelon plantsaccording to claim 53, wherein planting of said pollenizer watermelonplant is at a ratio of approximately equal to or less than 1 pollenizerwatermelon plant to 2 triploid watermelon plants.
 55. A method ofincreasing the yield of triploid watermelon plants according to claim53, wherein planting of said pollenizer watermelon plant is at a ratioof approximately equal to or less than 1 pollenizer watermelon plant to4 triploid watermelon plants. 56-68. (canceled)